I want to play the indoor version. What requirements must the indoor location meet?

In principle, any indoor location can be used, as long as you fit all the players in there.

Make sure there are 9 places where you can hide a QR code the size of an A4. Think of the underside of a table or chair, the back of a door, etc.

The more the teams really have to look for the QR codes, the more fun it becomes. In this sense, a large location offers more possibilities! A group will be able to scan a code without another team immediately seeing it.